At present, a common display device is generally a thin film transistor liquid crystal display (TFT-LCD) or an organic light-emitting diode (OLED) display, the light emitted by such a display device forms a light field emitting in a manner of a sphere, and thus the display device has a relatively large light-emitting spherical angle in space.
However, because display devices have a relatively large light-emitting spherical angle in space, the light energy received by a human eye accounts for a very small part, and thus the utility rate of the light energy is relatively low. In recent years, with the fast development of all kinds of display devices, how to increase the utility rate of the light energy is paid more attention by people.